Low-voltage connection with safety circuit and method for determining proper connection polarity

• US 8,199,024 B2
• Filed: 09/14/2009
• Issued: 06/12/2012
• Est. Priority Date: 11/28/2008
• Status: Expired due to Fees

• Current Assignee: Energy Process Technologies Incorporated (Energy Process Tech)
• Original Assignee: Energy Process Technologies Incorporated (Energy Process Tech)
• Inventors: Baxter, Jeffrey, Baxter, Brent, Baxter, Michael, Holbrook, Ted
• Primary Examiner(s): Nguyen, Phung
• Application Number:
  US12/559,357
• Publication Number:
  US 20100283623A1
• Time in Patent Office: 1,002 Days
• Field of Search: 340/687, 340/636.1, 340/636.12, 340/636.2, 361/93.9, 361/101
• US Class Current: 340/687
• CPC Class Codes: H01R 13/641 by indicating incorrect coupling; by indicating correct or full engagement
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/0034 using reverse polarity correcting or protecting circuits mechanical means of polarity protection H02J7/0045

Abstract

A safety circuit used in low-voltage connecting systems leaves the two low-voltage systems disconnected until it determines that it is safe to make a connection. When the safety circuit determines that no unsafe conditions exist and that it is safe to connect the two low-voltage systems, the safety circuit may connect the two systems by way of a “soft start” that provides a connection between the two systems over a period of time that reduces or prevents inductive voltage spikes on one or more of the low-voltage systems. When one of the low-voltage systems has a completely-discharged battery incorporated into it, a method is used for detection of proper polarity of the connections between the low-voltage systems. The polarity of the discharged battery is determined by passing one or more test currents through it and determining whether a corresponding voltage rise is observed.

Claims

1. A safety circuit for use in establishing connections between low-voltage systems to transfer energy from a first low-voltage system to a second low-voltage system, comprising:

a pair of input terminals;

a pair of output terminals;

a detection circuit operatively connected to the input terminals and the output terminals for detecting whether the input terminals and the output terminals are properly connected to first and second low-voltage systems, respectively;

a connection-controlling circuit configured to electrically connect the input terminals to the output terminals only when a proper connection has been detected and using a soft start procedure that reduces inductive voltage spikes; and

a transistor protection s stem for protecting transistors used to electrical connect the input terminals to the output terminals, the transistor protection system comprising a microcontroller that maintains a thermal model of heating of the transistors when power is flowing and a thermal model of cooling of the transistors when power is not flowing, that monitors for over-current conditions that could destroy the transistors, and that monitors for under-voltage conditions on the supply side.

2. A safety circuit as recited in claim 1, wherein the connection-controlling circuit controls one or more power transistors that are used to electrically connect the input terminals to the output terminals using the soft start procedure.

3. A safety circuit as recited in claim 2, wherein the soft start procedure connects the first low-voltage system to the second low-voltage system over a period of tens of milliseconds.

4. A safety circuit as recited in claim 1, wherein the safety circuit is incorporated into a jumper cable.

5. A safety circuit as recited in claim 1, wherein the safety circuit is incorporated into a battery charger.

6. A safety circuit as recited in claim 1, wherein the safety circuit is incorporated into a battery boost.

7. A safety circuit as recited in claim 1, further comprising a discharged battery test circuit configured to supply a test current to the output terminals and measure a resulting voltage to determine a proper polarity of a discharged battery connected to the output terminals.

8. A safety circuit as recited in claim 7, wherein the discharged battery test circuit is configured to supply test currents of different directions and to compare the voltages caused by the test currents.

9. A safety circuit as recited in claim 1, wherein the safety circuit is configured to detect whether a battery is connected to one of the pair of input terminals and the pair of output terminals by biasing the desired terminals to a voltage unlikely to occur naturally in one of the low-voltage systems and determining whether the voltage aberrates from the biased voltage by a given amount.

10. A safety circuit as recited in claim 1, wherein the safety circuit is configured to discriminate between a short circuit and a discharged battery by measuring the rise and fall time of a voltage measured across one of the pair of input terminals and the pair of output terminals as a limited current is allowed to flow.

11. A method of testing a polarity of a discharged battery connected to a first low-voltage system comprising:

connecting a test current source to a first low-voltage system containing a discharged battery;

supplying a first test current to the first low-voltage system;

measuring a first resulting voltage of the first low-voltage system;

supplying a second test current to the first low-voltage system, wherein the second test current is in an opposite direction to the first low-voltage system; and

measuring a second resulting voltage of the first low-voltage system.

12. A method as recited in claim 11, further comprising making an electrical connection between the first low-voltage system and a second low-voltage system only if the first resulting voltage exceeds a predetermined threshold voltage.

13. A method as recited in claim 11, further comprising making an electrical connection between the first low-voltage system and a second low-voltage system only if only one of the first resulting voltage and the second resulting voltage exceeds a predetermined threshold voltage and if the electrical connection will be of a proper polarity indicated by the measured first and second resulting voltages.

14. A method as recited in claim 11, wherein the method is incorporated as a test method upon connection of a battery charger to a system having a discharged battery.

15. A method as recited in claim 14, wherein the system having a discharged battery is a vehicle.

16. A method as recited in claim 11, wherein the method is incorporated as a test method upon connection of a battery boost to a system having a discharged battery.

17. A method as recited in claim 11, wherein the method is incorporated as a test method upon connection of a jumper cable to a vehicle having a discharged battery.

18. A jumper cable for use in establishing connections between low-voltage systems to transfer energy from a first low-voltage system to a second low-voltage system, comprising:

a safety circuit comprising;

a pair of input terminals;

a pair of output terminals;

a detection circuit operatively connected to the input terminals and the output terminals for detecting whether the input terminals and the output terminals are properly connected to first and second low-voltage systems, respectively;

a connection-controlling circuit configured to electrically connect the input terminals to the output terminals only when a proper connection has been detected and using a soft start procedure that reduces inductive voltage spikes; and

a transistor protection system for protecting transistors used to electrically connect the input terminals to the output terminals, the transistor protection system comprising a microcontroller that maintains a thermal model of heating of the transistors when power is flowing and a thermal model of cooling of the transistors when power is not flowing, that monitors for over-current conditions that could destroy the transistors, and that monitors for under-voltage conditions on the supply side;

a first cable connected to the input terminals and comprising first contact clamps for connecting to the first low-voltage system; and

a second cable connected to the output terminals and comprising second contact clamps for connecting to the second low-voltage system.

19. A jumper cable as recited in claim 18, wherein the safety circuit is contained in a control box proximate one of the first contact clamps and the second contact clamps.

20. A jumper cable as recited in claim 19, wherein the control box comprises a plurality of light emitting diodes for signaling conditions detected by the safety circuit to a user of the jumper cable.